This invention relates to a novel analytical test device for analysis of biological fluids such as urine. The invention further relates to methods for detecting analytes in fluids using the test device.
The sampling and testing of biological fluids such as urine for the presence of analytes provide important information regarding various health-related matters, including pregnancy and conception.
In recent years, test devices have undergone nearly continuous refinement in an effort to simplify and speed the process of detecting selected ligand in fluids. As a result of this work, current test devices use an immunoassay for determining pregnancy or conception. In these devices a reagent, such as an antibody, specifically reacts with an analyte to form a complex, which can usually be detected by the unaided eye.
Current pregnancy test devices assay for hormones associated with pregnancy, such as, for example, chorionic gonadotrophin (hereinafter xe2x80x9chCGxe2x80x9d) since the presence of hCG in urine is usually an indicator that a woman is pregnant. Such test devices obtain qualitative results indicating either the presence or absence of hCG. Typically, a pregnancy immunoassay contains an antibody directed against hCG. The reaction complex can then be viewed by the user.
Conception test devices also assay for hormones associated with the ovarian cycle, such as, for example, luteinizing hormone (hereinafter xe2x80x9cLHxe2x80x9d). LH is present normally in urine but its concentration increases markedly during ovulation, the time at which a woman is most likely to conceive. Thus, the probability that a woman can conceive a child varies directly with LH concentration. Such test devices obtain semi-quantitative results regarding the relative concentration of LH in the urine. Typically, a conception immunoassay contains an antibody directed against LH and a separate detection antibody.
In known devices, the fluid to be tested wicks up through an absorbent membrane that is in fluid flow contact with the reagents that detect an analyte in a fluid. A major problem with this type of device is that as the fluid progresses through the membrane, the front edge of the fluid is uneven. The uneven fluid front will cause the results to be smeared, produce false negatives and make the results difficult to detect. These artifacts are called xe2x80x9cleading edge effects.xe2x80x9d An uneven fluid front can arise for a variety of reasons, for example, because the sample is not uniformly applied to the absorbent membrane.
Therefore, a need exists for a device that does not produce an uneven fluid front and associated leading edge effects. The present invention provides a device that eliminates the uneven fluid front problem and related methods of using such a device.
The present invention provides an analytical test device for analyzing biological fluids, for example, urine. The device has a top with one or more display ports, and optionally, a sample aperture, an entry port and a vertical bar. The device also has a bottom with an upper plane, a slope and a contacting surface attached to the slope at a descending angle, optionally, a lower plane between the slope and contacting surface and, optionally, an entry port. The device further has a strip made up of an absorbent membrane, a reaction membrane with one or more reagents that form a reaction complex with an analyte in a fluid sample and, optionally, a collecting pad.
The absorbent membrane, the reaction membrane and the collecting pad, when present, are in fluid flow contact with one other. The strip is placed on the bottom such that the reaction membrane is visible through the display port and the absorbent membrane is on the slope and on the lower plane when present. The fluid sample contacts the absorbent membrane by first contacting the contacting surface when the top and bottom are assembled.
In one embodiment, the analytical test device has the contacting surface extending outward from the bottom. Here the absorbent membrane is in fluid flow contact with the contacting surface through the entry port. The top also has a vertical bar that deflects the absorbent membrane to the follow the contour of the slope.
The present invention also provides methods for detecting an analyte in a fluid sample, comprising contacting the fluid sample to the contacting surface of the analytical test device and detecting the analyte by observing the reaction complex through the display port. In one method the reaction complex is visible.